Hypofunctioning thyroid nodules

From a functional point of view, euthyroid diffuse goiter and hypofunctional thyroid nodules have to be discerned from hyperthyroid conditions, mainly toxic adenoma and toxic multinodular goiter. 

Thyroid scintigraphy separates hyperfunctioning (hot) and hypofunctional (cold) nodules. Hypofunctioning nodules are much more likely to harbor mafignancy than hyperfunctioning nodules. 

Perhaps the most important requirement of an instrument for thyroid scanning is its ability to detect small hypofunctioning (cold) nodules. This property depends not only on the actual site of the nodule but also on the ratio of activity within the hypofunctioning nodule and the surrounding tissue. This was tested with a phantom containing gelatin as tissue-equivalent material as previously described. The results are demonstrated in Table 2. 

For a hypofunctioning nodule, in the presence of iodine deficiency, probability of thyroid cancer is estimated to be in the range of 3—8%. This is a much lower figure than in areas with sufficient iodine supply. As a consequence, diagnosis and treatment considerations may differ in iodine-deplete and iodine-rich regions and have to be adapted accordingly. 

In hypofunctional nodules, discrimination between rare malignant and frequent benign thyroid lesions is a major challenge. 

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